Deploying IP Telephony with EX-series Switches · PDF fileDeploying IP Telephony with...

Application Note

Juniper Networks, Inc.1194 North Mathilda AvenueSunnyvale, California 94089 USA408.745.20001.888 JUNIPERwww.juniper.net

Deploying IP Telephony with EX-Series SwitchesOptimizing VoIP Applications with EX 3200 and EX 4200 Series Ethernet Switches

Part Number: 350131-003 Aug 2008

Copyright ©2008, Juniper Networks, Inc.2

Deploying IP Telephony with EX-Series Switches

Table of ContentsIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Description and Deployment Scenario—Method 1: VoIP Phones and End Hosts Sharing Ports . . . . . 3

VoIP Phones with LLDP-MED Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

VoIP Phones with LLDP-MED Support—Vendor and Model List . . . . . . . . . . . . . . . . . . . . . . . . . 4

Avaya LLDP-MED VoIP phone models: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Cisco Systems LLDP-MED VoIP phone models: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Nortel LLDP-MED VoIP phone models: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

LLDP and LLDP-MED Interaction with EX-Series Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Using Voice VLAN Support with LLDP-MED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Phones without LLDP-MED Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Using Access Port with Voice VLAN Feature (but without LLDP-MED) . . . . . . . . . . . . . . . . . . . . 13

Using Access Port with the Same VLAN ID for Both Voice and Data . . . . . . . . . . . . . . . . . . . . . 13

Using Trunk Port with Native-VLAN Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Description and Deployment Scenario—Method 2: Separate Ports for VoIP Phone and

Endpoint Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Assigning Each Port as Access Port for Different VLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Assigning Both Ports as Access Ports for Data VLAN with Voice VLAN Feature . . . . . . . . . . . . . 16

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

About Juniper Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Copyright ©2008, Juniper Networks, Inc. 3


IntroductionThe new EX-series Ethernet switches from Juniper Networks offer a number of features for optimizing IP telephony deployments . This application note describes how voice over IP (VoIP) phones can be deployed in conjunction with endpoint hosts such as desktop or laptop computers; provides background information on Link Layer Discovery Protocol (LLDP) and LLDP-Media Endpoint Discovery (LLDP-MED); and describes the interaction between VoIP phones and EX-series switches .

ScopeWhile this document can’t cover all of the physical configurations that are possible on EX-series switches, it does present configuration examples for the most common applications seen today . In particular, this document addresses configurations relating to:

• VoIPphonesandendpointhostssharingthesameswitchport

• UsingseparateportsforVoIPphonesandanendpointhost

This application note focuses on the Juniper EX 3200 and EX 4200 series switches as the solution for existing and new enterprise IP telephony deployments .

Description and Deployment Scenario—Method 1: VoIP Phones and End Hosts Sharing Ports

The most common enterprise VoIP edge deployment consists of VoIP phones and end-host machines connected in series and attached to a single switch port . This physical layout reduces switch port requirements by allowing multiple end user devices to share a connection rather than occupy their own individual switch ports, thereby reducing the total number of switches deployed, as well as capital and operational expenses .

However, when VoIP phones and end hosts share a switch port, sound quality on an IP phone call will suffer when large bursts of data traffic create network congestion that leads to packet loss or delay . To overcome this problem, it is desirable to provide voice traffic with a higher level of service due to its susceptibility to jitter, delay and packet loss .

Figure 1. VoIP Phone and End-Host Machine Sharing a Switch Port

This is accomplished by separating voice and data traffic into separate broadcast domains or VLANs—an essential capability for any robust VoIP solution . The EX-series switches offer a Voice VLAN feature that enables otherwise standard access ports to accept both untagged (data) and tagged (voice) traffic from directly connected VoIP phones, and separate these traffic streams into separate VLANs (namely data-VLAN and voip-VLAN) .

The EX-series switches can separate data and voice traffic on the switch port where Voice VLAN is implemented . However, the phone is still vulnerable to large bursts of data from the attached end host on its own phone port, depending on the phone’s ability to prioritize its own voice traffic over the end-host data traffic before forwarding both streams to the switch . To solve this problem, the user can take the “separate port” approach in which the phone and the end host are connected to separate ports on the switch . This solution is covered in the “Method 2” section of this paper .

EX-series



VoIP Phones with LLDP-MED SupportBefore exploring the actual interaction between VoIP phones and the EX-series switch, it’s important to understand the fundamentals of two industry-standard protocols: Link Layer Discovery Protocol (LLDP) and LLDP-Media Endpoint Discovery (LLDP-MED) . This section will provide a brief overview covering the basics of these two protocols .

LLDP, also known as IEEE 802 .1AB, is a standards-based Layer 2 protocol that allows network devices to advertise and receive their identity and capabilities on a LAN segment, most of them directly connected . This protocol, developed as an open standard, was modeled after various vendor-specific proprietary discovery protocols such as Cisco Discovery Protocol (CDP), Extreme Discovery Protocol (EDP), Nortel Discovery Protocol (NDP) and others . The Juniper Networks EX-series switches have embraced the open, standards-based LLDP as their Layer 2 discovery protocol .

LLDP-MED is an extension to the IEEE 802 .1AB standard published by the Telecommunications Industry Association (TIA) . This standard, ANSI/TIA-1057, is designed to support interoperability between VoIP endpoint devices and other networking end-devices, focusing mainly on discovery to facilitate information sharing between endpoints and network infrastructure devices . Some of the benefits of LLDP-MED include:

Network policy discovery• that allows endpoints and switches to advertise their VLAN IDs (for example, voip-VLAN), Layer 2 Priority and Differentiated Services Code Point (DSCP)

Power over Ethernet (PoE) management• that allows endpoint devices to advertise their actual PoE levels and enables power sourcing equipment (like switches) to budget their power allocation accordingly

Inventory management discovery • that stores endpoint device information such as vendor, model firmware and serial number on the switch and makes it accessible to network management systems for inventory reporting purposes

VoIP Phones with LLDP-MED Support—Vendor and Model List Some VoIP phone vendors and their respective LLDP-MED-compatible VoIP phones are listed below . The information in this section, current as of May 2008, has been gathered from publicly available sources such as vendor Web sites . To confirm the latest VoIP phones with LLDP-MED support, consult each vendor’s product documentation .

Avaya LLDP-MED VoIP phone models:9600 Series with firmware release 1 .2 .1•

4600 Series with firmware release 2 .6•

Cisco Systems LLDP-MED VoIP phone models:7906G•

7911G•

7931G•

7941G/7941G-GE•

7942G•

7945G•

7961G/7961G-GE•

7962G•

7965G•

7970G/ 7971G-GE•

7975G•



Nortel LLDP-MED VoIP phone models:IP Phone 1110•

IP Phone 1120E with firmware version 0624C23•

IP Phone 1140E with firmware version 0625C23•

IP Phone 1150E•

IP Phone 1210•

IP Phone 1220•

IP Phone 1230•

IP Phone 2001 with firmware version 0604DAD•

IP Phone 2002 Phase 2 with firmware version 0604DAD•

IP Phone 2004 Phase 2 with firmware version 0604DAD•

IP Phone 2007 firmware version 0621C3A•

LLDP and LLDP-MED Interaction with EX-Series SwitchesWhile LLDP and LLDP-MED help simplify IP telephony deployments, it is important to understand how they interact with the VoIP phones and switches—specifically with the EX-series switches, which will not advertise their capabilities via LLDP-MED when a port is first brought online .

Figure 2 provides an overview of the LLDP/LLDP-MED message exchange sequence when an LLDP-MED-enabled VoIP phone is first connected to a switch port on an EX-series switch .

Figure 2. LLDP and LLDP-MED Interaction Between EX-Series Switch and VoIP Phone

Figure 3. An EX-Series Switch Sending Out LLDP Data Unit

EX-series2

3

1Interface will start advertising Base LLDP

LLDP-MED advertisement sent by neighbor

EX switch will toggle to LLDP-MED



This interaction can be seen in detail in the highlighted section of the packet capture shown in Figure 3 . Note that LLDP, as defined in IEEE 802 .1AB, sends the data unit to a well-known IEEE multicast address (01:80:c2:00:00:0e) . This address is defined within a range of addresses reserved by the IEEE for protocols that are to be confined to an individual LAN segment .

On the other hand, LLDP-MED-capable VoIP phones will advertise their capabilities using LLDP-MED from the start . Note that the fields within the section named TIA indicate LLDP-MED (Figure 4) .

Figure 4. LLDP-MED-Capable VoIP Phone Sending LLDP-MED Data Unit

Upon receiving the LLDP-MED data units from the neighboring end device (VoIP phone), the EX-series switch will start advertising its capabilities using LLDP-MED (Figure 5) .



Figure 5. EX-Series Switch Sending LLDP-MED Data Unit Upon Receiving LLDP-MED-Capable Endpoint

Using Voice VLAN Support with LLDP-MEDAs mentioned earlier, the Voice VLAN feature enables EX-series switches to accept both untagged (data) and tagged (voice) traffic from directly connected VoIP phones, and split these traffic streams into different VLANs . This feature delivers its greatest benefit when connected to a VoIP phone capable of advertising and receiving LLDP-MED data units, including VLAN ID assignments, because it essentially enables the EX-series switch to deliver a “plug-and-play” IP telephony solution (Figure 6) .

Figure 6. LLDP-MED-Capable VoIP Phone in a Shared Switch-Port Physical Layout

EX-series

Data VLAN 10 Voice VLAN 99

LLDP-MED

Access Portwith Voice

VLAN feature



The following section details the implementation shown in Figure 6 .

The configuration of EX-series switches with the Voice VLAN feature in a typical shared switch-port implementation with LLDP-MED-capable VoIP phones is as follows:

user@switch# set protocols lldp interface all

user@switch# set protocols lldp-med interface all

user@switch# set vlans voip-only vlan-id 99

user@switch# set vlans data-only vlan-id 10

user@switch# set interfaces ge-0/0/1 unit 0 family ethernet-switching port-mode access

user@switch# set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan member data-only

user@switch# set ethernet-switching-options voip interface ge-0/0/1.0 vlan voip-only

user@switch# set ethernet-switching-options voip interface ge-0/0/1.0 forwarding-class expedited-forwarding

user@switch# commit

Although these strings of data may appear overwhelming to someone who is unfamiliar with JUNOS™ software, the Juniper Networks operating system, the configuration semantics are actually very straightforward . A closer inspection of the individual functional blocks will help explain what is happening and clarify the benefit of the Voice VLAN feature .

In the first functional block (below), the protocols to be used—LLDP and LLDP-MED—are turned on . Although these protocols are turned on by default on any EX-series switch, it is specifically called out here for clarification .

user@switch# set protocols lldp interface all

user@switch# set protocols lldp-med interface all

In the second functional block (below), two VLANs are defined: one for voice and one for data . The actual VLAN IDs used on this example are arbitrary; the EX-series switch allows VLAN ID configurations up to 4096 .



In the third functional block (below), the interface “ge-0/0/1” has been configured as an access port belonging to the data VLAN (“data-only”) . Notice that there is no configuration needed for the voice VLAN, which is covered in the next section .


user@switch# set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan member data-only



In the fourth functional block (below), the Voice VLAN feature is configured under the Ethernet-switching-options stanza with the voip option (see the “ethernet-switching-options voip” command below) . Here the actual VLAN to be used for voice will be defined, as well as the level of service that will be provided for traffic received on that VLAN—in this example, “expedited-forwarding .”

user@switch# set ethernet-switching-options voip interface ge-0/0/1.0 vlan voip-only

user@switch# set ethernet-switching-options voip interface ge-0/0/1.0 forwarding-class expedited-forwarding

In the fifth functional block (below), the configuration is committed in JUNOS, making it active .

user@switch# commit

Upon completion, the LLDP-MED configuration can be verified on the EX-series switch, as shown below .

user@switch> show lldp

LLDP : Enabled

Advertisement interval : 30 seconds

Transmit delay : 2 seconds

Hold timer : 4 seconds

Config Trap Interval : 60 seconds

Connection Hold timer : 300 seconds

LLDP MED : Enabled

MED fast start count : 3 Packets

Interface LLDP LLDP-MED

all Enabled Enabled



Advertisements sent by neighboring VoIP phones can also be viewed . A Cisco VoIP phone was used for the following example:

user@switch> show lldp neighbors interface ge-0/0/1.0

LLDP Neighbor Information:

Index: 1 Time to live: 180 Time mark: Thu Mar 6 22:35:53 2008 Age: 28 secs

Local interface : ge-0/0/1.0

Chassis type : Network address

Chassis ID : 172.16.10.10

Port type : Locally assigned

Port ID : xxxxxxxxxxxx:P1

Port description : SW PORT

System name : SEPxxxxxxxxxx

System description : Cisco IP Phone CP-7945G,V1, SIP45.8-3-3SR2S

System capabilities

Supported: Bridge Telephone

Enabled : Bridge Telephone

Management address

Type : IPv4

Address : 172.16.10.10

Media endpoint class: Class III Device

MED Hardware revision : 1

MED Firmware revision : tnp45.8-3-1-21.bin

MED Software revision : SIP45.8-3-3SR2Sbin

MED Serial number : xxxxxxxxxxxxxxxx

MED Manufacturer name : Cisco Systems, Inc.

MED Model name : CP-7945Gstem

MED Asset id : CP-7



By using a packet capture tool, the details of the actual interaction between the EX-series switch and LLDP-MED-capable VoIP device can be viewed (see Figures 7 through 10) .

Figure 7. LLDP Data Unit Advertised by EX-Series Switch

As discussed previously regarding the interaction between LLDP and LLDP-MED, the EX-series switch will initially advertise its capabilities using LLDP only, as shown in Figure 7 . The LLDP-MED-capable phone will advertise its capabilities using LLDP-MED, as shown in Figure 8 . A Cisco IP phone 7945G was used in the following example .

Figure 8. LLDP-MED-Capable VoIP Phone Advertising Its Capabilities

Sections preceded with a TIA heading show that the VoIP phone is LLDP-MED-capable; its media capabilities and network policy can also be viewed . Note that the VLAN ID sent by the VoIP phone shows the voice VLAN ID as 0 with a Layer 2 (802 .1p) priority of 5 for voice traffic and a VLAN ID of 0 with a Layer 2 (802 .1p) priority of 4 for voice-signaling traffic .



Figure 9. EX-Series Switch Advertising Network Policy for VoIP Phone via LLDP-MED

Once the EX-series switch determines that the connected device is LLDP-MED-capable, it will advertise its capabilities and defined network policy via LLDP-MED . In Figure 10, the VLAN ID used for voice is set at 99 as configured .

Figure 10. LLDP-MED-Capable Phone Advertising Changed Network Policy per EX-Series Switch

The LLDP-MED-capable VoIP phone now sets VLAN ID 99 for both voice and voice-signaling traffic in its LLDP-MED network policy in response to the LLDP data unit it received previously .



Phones without LLDP-MED SupportWhile organizations can derive great benefits by using LLDP-MED-capable VoIP phones, the fact is that most existing VoIP deployments don’t support the protocol, and businesses are unlikely to incur the cost required to upgrade these devices . In such cases, there are several other IP telephony methods available that the EX-series switches can support . Each of these solutions, however, has some unique requirements .

Using Access Port with Voice VLAN Feature (but without LLDP-MED)Although the Voice VLAN feature delivers the greatest benefit when coupled with LLDP-MED-capable VoIP phones, it is flexible enough that non-LLDP-MED-capable phones can also use it effectively . However, such a configuration requires that the Voice VLAN feature be set manually on the VoIP phones themselves, since LLDP-MED is not available to accomplish this dynamically .

Figure 11. Access Port with Voice VLAN Feature

Once the Voice VLAN ID and other relevant parameters have been manually set on the VoIP phone to match the settings configured on the EX-series switch, the feature behaves the same as it does when configured with LLDP-MED-capable VoIP phones .

Using Access Port with the Same VLAN ID for Both Voice and DataAnother way to deploy an IP telephony solution is to assign both the VoIP phone and the end-host machine to a single VLAN . This is the simplest configuration among the methods discussed in this document .

Figure 12. Both VoIP Phone and Endpoint Device in the Same VLAN

The configuration is performed as follows:

user@switch# set vlans voice-and-data vlan-id 100


user@switch# set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan member voice-and-data

user@switch# commit

EX-series

Data VLAN 10 VoIP VLAN 99

Non-LLDP-MED


VLAN feature

EX-series

VLAN 100 VLAN 100

Non-LLDP-MED



Although this method is technically feasible, it is not a recommended configuration because placing both data and voice traffic on the same VLAN leaves the voice traffic prone to potential jitter, delay and packet loss—conditions that are introduced by “bursty” data traffic .

Using Trunk Port with Native-VLAN OptionUsing a switch trunk port where the VoIP phone and endpoint host are connected will create the desired separation between voice and data traffic, but it requires some additional configuration on both the switch and the VoIP phone .

Figure 13. Trunk Port with Native-VLAN Option

A sample trunk configuration is provided below:



user@switch# set interfaces ge-0/0/1 unit 0 family ethernet-switching port-mode trunk

user@switch# set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan member [ voip-only ]

user@switch# set interfaces ge-0/0/1 unit 0 family Ethernet-switching native-vlan-id data-only

user@switch# commit

Let’s look at this particular configuration in greater detail . Similar to the Voice VLAN feature, two VLANs are configured here: voip-only and data-only .

user@switch# set interfaces ge-0/0/1 unit 0 family ethernet-switching port-mode trunk

user@switch# set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan member [ voip-only ]

However, in this case the interface is configured as a trunk that includes only the voice VLAN . In order to separate the voice and data traffic, the trunk port will transmit and receive only tagged traffic on the trunk VLAN member list, which in this case is the voip-only VLAN .

EX-series

Untagged VoIP VLAN 99

Non-LLDP-MED

Trunk Port withNative VLAN -

VoIP VLAN



Since a typical endpoint host such as a desktop or laptop will send its packets untagged (which will subsequently be relayed by the VoIP phone), the corresponding switch trunk port must be configured with the “native-vlan-id” option in order to transmit and receive untagged traffic belonging to the native VLAN, which in this case is the data-only VLAN . Otherwise, untagged packets sent from the endpoint host and relayed by the phone would be dropped on the switch trunk port by default, since the packets are untagged .

user@switch# set interfaces ge-0/0/1 unit 0 family Ethernet-switching native-vlan-id data-only

Description and Deployment Scenario—Method 2: Separate Ports for VoIP Phone and Endpoint Device

Figure 14. Separate Ports for VoIP and Endpoint Device.

In contrast to the shared switch-port configuration discussed earlier, VoIP phones (LLDP-MED-capable and non-capable) and endpoint hosts can also occupy their own ports . This is not a typical IP telephony deployment in the enterprise today, where cost reduction is a priority, but there are cases where endpoint devices would occupy their own ports, mainly for management, troubleshooting and maintenance purposes .

Assigning Each Port as Access Port for Different VLANWhen attaching VoIP phones and endpoint devices to their own ports, one approach is to assign each port to different VLANs, so that the port connected to the VoIP phone is configured for voice traffic and the port connected to the endpoint host is configured for data traffic .

EX-series

Voice



Figure 15. Each Port as Access Port for Different VLAN

This configuration is very straightforward; examples discussed previously in this document can be used as reference . Furthermore, this method does not require any manual settings on either the VoIP phone or the endpoint host, as they already belong to the correct domain as soon as they are physically connected .

Assigning Both Ports as Access Ports for Data VLAN with Voice VLAN FeatureAnother two-port option is to assign both ports (where the VoIP phone and endpoint host are connected) into the data VLAN and then configure the Voice VLAN feature . Manual configuration may be required if the VoIP phone is not LLDP-MED-capable . The actual configuration is very similar to the configuration shown in the Access Port with Voice VLAN section .

Figure 16. Both Ports as Access Ports of Data VLAN with Voice VLAN Feature

EX-series

VoIP VLAN 99

Data VLAN 10

Voice

EX-series

VoIP VLAN 99

Data VLAN 10

Voice


VLAN feature



SummaryWhen implementing an IP telephony solution, there are a number of options to consider before committing to the actual deployment . This application note has discussed a variety of methods for implementing an IP telephone solution, including the physical layout of VoIP phones and endpoint devices, the Voice VLAN feature of the EX-series switches, LLDP and LLDP-MED, and more . These methods and technologies can and will make a difference in the successful implementation of an IP telephony solution .

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Copyright 2008 Juniper Networks, Inc. All rights reserved. Juniper Networks, the Juniper Networks logo, JUNOS, NetScreen, and ScreenOS are registered trademarks of Juniper Networks, Inc. in the United States and other countries. JUNOSe is a trademark of Juniper Networks, Inc. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners. Juniper Networks assumes no responsibility for any inaccuracies in this document. Juniper Networks reserves the right to change, modify, transfer, or otherwise revise this publication without notice.

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About Juniper NetworksJuniper Networks, Inc . is the leader in high-performance networking . Juniper offers a high-performance network infrastructure that creates a responsive and trusted environment for accelerating the deployment of services and applications over a single network . This fuels high-performance businesses . Additional information can be found at www .juniper .net .

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